This invention relates to apparatus for harvesting root crops and more particularly to such apparatus wherein a root crop of round or bulbous roots such as onions or garlic is reliably separated from a mixture of the root crop, dirt and debris which is picked up by the apparatus as it moves over a cultivated field in which the root crop is grown.
Root crop harvesters have been known in the prior art. Such prior art harvesters have incorporated various light sources and photoelectric cells to separate the root crop from the mixture of root crop, dirt and debris which is picked up by those harvesters. Illustrative of prior art root crop harvesters is the apparatus shown in U.S. Pat. No. 4,082,189 issued Apr. 4, 1978.
In this prior art harvester, a mixture of unearthed root crop and associated dirt and debris is lifted from the surface of a cultivated field and passed over a series of various conveying devices which serve to separate some of the dirt and debris from the mixture. The resulting mixture of root crop, dirt and debris is passed to an ultimate stage of conveyors which serve to "singularize" the root crop. Individual articles of the root crop and clump form dirt and debris are singularized into single file rows of articles which are supported in singularizing grooves formed between multiple rows of special narrow singulator belts mounted on the harvester. A plurality of incandescent lamps are focused through the singularizing grooves to strike articles of the mixture which are carried on the singulator belts. A plurality of photoelectric cells corresponding to the plurality of incandescent lights are positioned to receive light reflected from singularized articles of the mixture carried by the singulator belts and subjected to the focused incandescent light. The individual articles are identified and discriminated by the light which they reflect to the photoelectric cells. Articles identified as root crop product are passed to a root crop product conveyor while articles identified as dirt and debris are actively rejected in response to a signal from corresponding photoelectric cells to a dirt and debris rejection conveyor.
The active rejection of articles identified as dirt and debris is performed by air jets or mechanical fingers located within the singularizing grooves formed between the singulator belts. The air jets or mechanical fingers are controlled in response to signals generated by the photoelectric cells associated with the grooves formed by the singulator belts. The rejection air jets or fingers are located downstream from the photoelectric cells and are operated a defined period of time after the light reflected from singularized articles is sensed and the articles are identified as dirt and debris by the respective photoelectric cells. The operation of the rejection air jets or fingers is coordinated with the movement of the singulator belts. On operation, the air jets or fingers respectively blow or impact articles identified as dirt and debris to change the falling trajectory of the articles and divert them onto a dirt and debris conveyor which then conveys the articles to the side of the harvester where they are discharged back to the surface of the cultivated field. If the articles are identified by the photoelectric cells as root crop, the corresponding air jets or fingers are not activated and the articles so identified are allowed to fall onto the root crop conveyor.
The use of the singulator belts provided on the prior art harvester are a costly expedient and as the belts wear and must be replaced, the time required to replace multiple singulator belts is both lengthy and costly. Furthermore, the use of active rejection of dirt and debris for all root crops is undesirable. The use of active rejection for root crops harvested in a dry condition, such as onions, tends to disintegrate the rejected articles and allow small particles of dirt and debris to fall onto the root crop conveyor. This dirt and debris is passed with the roots to product cartons making the root crop product less desirable by virtue of its incomplete separation and such added dirt and debris adds to shipping weights.